We developed a novel near-infrared (NIR) fluorescent probe, GPU-167, for in-vivo imaging of tumor hypoxia. GPU-167 comprises a tricarbocyanine dye as an NIR fluorophore and two 2-nitroimidazole moieties as exogenous hypoxia markers that undergo bioreductive activation and then selective entrapment in hypoxic cells.
After treatment with GPU-167, tumor cells contained significantly higher levels of fluorescence in hypoxia than in normoxia. In-vivo fluorescence imaging specifically detected GPU-167 in tumors 24 h after administration. Ex-vivo analysis revealed that fluorescence showed a strong correlation with hypoxia inducible factor (HIF)-1 active hypoxic region. These data suggest that GPU-167 is a promising in-vivo optical imaging probe for tumor hypoxia.